This patent proposes a device for turning brake disks that includes an automatic compensation unit that functions to automatically compensate for runout between a lathe applied directly to the vehicle, and the brake disk to be turned.
The device according to this innovation has the advantage of being able to use an automatic alignment tool so that the job of turning the brake disks can even be entrusted to personnel without specific preparation or expertise. It also saves time compared to traditional manual systems.
It consists, in other words, of a device that allows totally automatic detecting of runout of the brake disk to be turned and consequently, using a suitable calculator, transforms signals coming from the detector into controls for an electromagnetic actuator that acts on a triad of rotating adjustment devices controlling the distance between the two faces of the alignment device.
As is known, disk brakes used on motor vehicles are subject to substantial frictional forces from brake caliper shoes, and undergo wear with the passage of time and periodically require replacement of the shoes and, if necessary, turning of the surface of the disk when the surface is found to be grooved by the shoes beyond admissible maximum values.
It is also known that the surface of the disk, in addition to the formation of grooves caused by shoe friction, is also subject to other forces that cause lateral warping of the disk. These abnormalities must also be detected and corrected during turning procedures since they could jeopardize the safety of the vehicle by generating dangerous vibrations during braking.
One of the main components of a vehicle wheel braking system employing disk brakes are the brake disks or brake rotors which provide a solid rotating surface against which the stationary brake friction pads are clamped or compressed to generate a frictional force, slowing the rotational movement of the brake disks or brake rotors and the associated vehicle wheels. These brake disks or brake rotors are subjected to repeated and substantial frictional forces by the brake friction pads, and over time, become worn. Uneven application of braking force, debris, or uneven frictional surfaces on the brake friction pads can result in the formation of grooves, channels, or scratches in the surfaces of the brake disks or brake rotors. Repeated heating and cooling of the brake disk or brake rotor resulting in extreme temperature variations can additionally result in the lateral warping of the brake disk or brake rotor.
A worn or warped brake disk or brake rotor may be resurfaced by cutting or grinding to provide a uniform smooth brake friction pad contact surface if sufficient brake disk or brake rotor material remains to provide an adequate braking surface without compromising the structural integrity of the vehicle braking system. However, once a brake disk or brake rotor has been worn below a minimum safe thickness, it is unable to safely dissipate the heat generated by a brake application, and must be replaced.
To provide for a uniform surface, any abnormalities in the brake disk or brake rotor, such as a lateral warping must be detected and compensated for during the resurfacing procedures. An additional source of lateral warping defects in a brake rotor or brake disk is often over tightened attachment bolts or an uneven mounting surface onto which the brake disk or brake rotor is secured in the vehicle wheel assembly. If the brake disk or brake rotor is removed from the vehicle wheel assembly for a resurfacing operation, any abnormalities or defects resulting from the mounting of the brake disk or brake rotor to the vehicle wheel assembly may not be accurately identified or corrected during the resurfacing procedure. Accordingly, a variety of brake resurfacing machines or brake lathes have been developed to resurface brake disks and brake rotors while they remain mounted to the vehicle wheel assembly.
At the present time, to detect and correct warping of the disk surface, monitoring devices are used to determine disk runout and to correct disk deformations.
These devices are of various types although recently the sector has seen increasingly widespread use of lathes applied directly to the hub of the vehicle. These avoid the need to remove the brake disk and consequently speed up the entire repair process and also, in addition, perform repair with greater precision.
It is necessary for these devices that the lathe applied to the wheel be subsequently aligned with the axis of the wheel hub because the lathe is mounted on the axle using the wheel hub itself.
However, the wheel hub, either because of manufacturing defects or due to the presence of rust that forms at the points where the fastening screws are tightened or due to deformation caused by excessive tightening of the heel fastening screws, is never perfectly aligned with its own axle and this runout must be corrected in order to turn the brake disk.
Known equipment for turning brake disks generally include a support on which the lathe is mounted, a motor that drives the disk to be turned and an alignment and compensation device. This device may be manual or automatic depending on the model of the device.
If the alignment device is the manual type then the machine operator corrects for runout detected by optical or electronic devices by correcting suitable manual adjusters that align the lathe axis with that of the disk in order to perform correct turning.
This system has the problem that the operator who uses it must have a great deal of experience in correcting compensation parameters. As a consequence it is not suited for personnel without special expertise.
In the automatic version correction is no longer done manually but is done using special automatic detection and adjustment devices.
The main problem these devices present is the difficulty they have in correctly detecting runout between the hub and the relative disk.
Brake resurfacing machines or brake lathes configured to resurface brake disks and brake rotors mounted to a vehicle wheel assembly are commonly referred to as on-car brake lathes. By eliminating the need to remove the brake disk or brake rotor from the vehicle wheel assembly, the overall efficiency of the resurfacing procedure is improved, and the chances for operator induced error are reduced. However, the resurfacing of brake disks and brake rotors which remain mounted to the vehicle wheel assembly requires that the on-car brake lathe and the vehicle wheel assembly, including the brake disk or brake rotor, be aligned along a common axis, typically, the axis of the vehicle wheel assembly hub onto which the on-car brake lathe is secured.
Often, the hub surface to which the vehicle wheel assembly mounts, is not aligned within a required tolerance to the axis of rotation for the axle upon which the vehicle wheel assembly is secured. This deviation between the hub surface and the axis of rotation for the wheel assembly is referred to as lateral runout, and must be compensated for either manually or automatically before beginning the resurfacing procedures with the on-car brake lathe.
Manual runout compensation procedures are tedious and complex. First, an operator secures the on-car brake lathe to the vehicle wheel hub using a suitable adapter. Next, a motor in the on-car brake lathe is activated to rotate the adapter and brake disk or brake rotor. Any runout present in the system is measured by one or more measurement devices, which provide the operator with a suitable visual indication representative of the actual runout experienced by the on-car brake lathe as the adapter is rotated through one or more complete rotations. Using the visual indication, the operator manually adjusts one or more mechanical adjustment elements, such as screws or dials, altering the rotational axis of the on-car brake lathe to reduce the observed runout to within an acceptable tolerance for performing the resurfacing of the brake disk or brake rotor.
To reduce the observed runout to within the desired tolerances using the manual runout compensation procedure usually requires several iterations when carried out by a skilled operator. The extra time spent by an operator to setup the on-car brake lathe and perform the manual runout compensation can substantially increase the time required to complete a brake disk resurfacing, resulting in a corresponding increase in cost and lost productivity.
Several solutions, such as that one relating to patents WO 98/10262 and WO 98/09754 registered on behalf of Joseph Willey, are known that have, for example, runout compensation devices where detection is performed by an accelerometer device which, after a certain number of revolutions, determines misalignment and the relative compensation plane to act on.
This system presents the problem of slowness in display of the amount of runout because the device must perform several revolutions to get in phase and determine the compensation plane even if runout is very small.
A number of on-car brake lathe devices have been configured with automatic runout compensation mechanisms which do not require significant operator input. One such automatic runout compensation mechanism is shown in U.S. Pat. No. 6,101,911 to Newell et al. (the ""911 Newell et al. patent). The automatic runout compensation mechanism shown in the ""911 Newell et al. patent includes at least one adjustment disc interposed between a pair of adapters and which is concentric about a axial drive shaft. The on-car brake lathe motor and cutting elements are secured to one adapter, and the entire mechanism secured to the vehicle wheel hub via the second adapter. The adjustment disc includes a slanted surface in engagement with either a second adjustment disc having an opposing slanted surface or one of the adapters. An adjustment mechanism is utilized to alter the rotational orientation of the adjustment disc about the axis of the axial drive shaft. Runout is detected by a rotational accelerometer, which provides control signals to the adjustment mechanism. Alteration of the rotation position of the adjustment disc about the axis of the axial drive shaft compensates for the detected runout by altering the angle at which the two slanted surfaces are engaged, and correspondingly the angle between the first and second adapters.
The adjustment mechanism of the ""911 Newell et al. patent associated with the use of the one or more slant discs is a complex mechanical arrangement, requiring initial phasing of the adjustment discs and a lengthy trial-and-error adjustment process to compensate for any detected runout.
Accordingly, there is a need for on-car brake lathes having improved automatic runout compensation mechanisms, and which can quickly and accurately compensate for detected runout.
The object of the present invention is to achieve an automatic runout compensation device for brake disk turning equipment which includes a system that is able to perform real detection of runout because it employs a direct feeler type of system and does not use an accelerometer device.
The innovation in question, as part of this general object, proposes use of a system that displays the amount of runout both during realignment and at the end.
The device according to the innovation offers the advantage of reducing alignment times because the aligning joint, since it can be zeroed before application, starts compensating from the very start of rotation unlike the known devices that must dedicate several revolutions to get in phase before they start.
In addition, according to the innovation and thanks to the possibility of zeroing the screws, alignment time becomes proportional to the runout that is detected so that realignment is practically instantaneous in case of small runout.
Another advantage of the innovation is the fact that no special attention is required when tightening the screws that fasten the lathe to the vehicle""s hub. These can be tightened all the way without fear of blocking the alignment mechanism.
The above-mentioned objects and advantages are all achieved, according to the invention, by a device for turning brake disks or the like that includes an automatic runout compensation unit, characterized by the fact that a special runout detecting device, at least one device for elaborating the centering device control signals and a special aligning joint are installed on the support that can be mounted on the hub of the vehicle and by the fact that this runout detecting device is composed of a linear movement detector preferably of the type with an electronic comparator using LVDT technology or the like.
Briefly stated, the present invention provides an on-car brake lathe system for the resurfacing of a brake disk or brake rotor which remains mounted to a vehicle wheel assembly. The on-car brake lathe system includes a lathe body, a drive motor, a cutting head, and a mounting chuck driven by the drive motor. The on-car brake lathe system further includes an aligning joint having a pair of mounting flanges concentrically disposed about the rotational axis of the mounting chuck, one of which is secured to the mounting chuck, and the other of which is configured for securing the on-car brake lathe system to a vehicle wheel assembly. An automatic runout compensation mechanism is disposed between the pair of flanges, securing the first flange and the second flange together at an adjustable inclination or alignment angle. The automatic runout compensation mechanism includes three discrete adjustment elements equidistantly disposed about the mounting chuck rotational axis, and is configured to adjust the relative inclination or alignment angle between the pair of flanges to provide runout compensation between the rotational axis of the drive shaft and the rotational axis of the vehicle wheel assembly.
In an embodiment of the on-car brake lathe system of the present invention, each adjustment element includes two opposing surfaces, each having an opposed helical channel, between which are contained a number of ball bearings. At least one of the opposing surfaces and corresponding helical channels is configured for controlled rotation about a central axis aligned parallel to the chuck rotational axis. As the opposing surface and helical channel rotate about the central axis, the ball bearings maintain a minimum spacing between the opposed helical channels, varying the spacing between the opposing surfaces in direct relation to the depth of the rotated helical channel. Displacement of the spacing between the opposing surfaces alters the relative alignment angle between the pair of flanges, providing for runout compensation.
In an embodiment of the on-car brake lathe system of the present invention, a linear variable differential transformer (LVDT) device is provided to generate signals representative of runout present in the mounting of the on-car brake lathe to a vehicle wheel hub. The signals representative of the detected runout are utilized to control the adjustment of each of the discrete adjustment elements to reduce the detected runout to within a required tolerance.
The foregoing and other objects, features, and advantages of the invention as well as presently preferred embodiments thereof will become more apparent from the reading of the following description in connection with the accompanying drawings.